Commercial diesel fuels contain impurities that can lead to deposition of solids and gums in engines during fuel combustion. Such engine deposit problems are of greater significance for diesel fuels than gasoline fuels because the diesel fuels generally contain greater concentrations of high molecular weight materials. The thermal breakdown of such materials forms insoluble deposits on the engine that can reduce operating efficiency and, ultimately, can lead to corrosion or blockage of fuel injectors and other critical working elements of an engine. Insoluble impurities may also be introduced from the external environment during processing, transport, or pumping of the fuel.
One desirable function of a fuel additive is to impart detergency properties upon the fuel mixture in order to prevent the unwanted deposition of solids during normal engine operation. Ideally, previously deposited materials may also be solubilized by an added detergent, potentially increasing engine performance. Materials imparting corrosion protection properties are additionally desirable in extending the lifetime of the engine.
Succinimide compounds have been used as detergents for fuel and lubricant formulations wherein the succinimide compounds are generally dissolved in a diluent fluid of oils or glycols. For example, U.S. Pat. No. 5,518,511 discloses the use of a gasoline detergent composition containing polyisobutylene succinimides and diluent oils such as mono end-capped polypropylene glycol, as well as other components such as anti-oxidants, dehazers, and deicers.
U.S. Pat. No. 5,334,228 discloses deposit control additives and fuel compositions containing polyalkenyl succinimides and diamondoid carrier fluids such as adamantane, diamantane, triamantane, and tetramantane. U.S. Pat. No. 5,114,435 discloses a composition containing a polyalkylene succinimide, a polyalkylene, and mineral oil for the removal and prevention of engine deposits for use in gasoline and diesel fuels. U.S. Pat. No. 5,264,004 discloses the reaction product of an aldehyde, a hydrocarbylsuccinimide dimer, and a heteroatom substituted benzoic acid as a multifunctional fuel and lubricant additive. The disuccinimide product is formulated with mineral oil, synthetic oil, or grease mixtures. U.S. Pat. No. 4,501,597 discloses the use of polyalkyleneamine succinimide oxamides as fuel detergents wherein at least 30% of amine moieties are derivitized with oxalic acid.
There is a need in the art for improved detergent additive compositions for diesel fuels that remove or prevent engine deposits and their corrosive effects.